Reply To: GV125C Tuning frustration
GV125C 2012I saw the youtube clip, hmmm i can try break this down for ya , follow me, i think i am on to something but will need you to also verify next time you have your hands on it.
- Spray the airbox rubbers and intake rubbers = see if revs change or engine grumbles or screams = air leak. [\quote] I did this earlier and no change (this also applied earlier too, i think my rubbers are good just the carb doing something funky) Also the biggest change to speed happened when putting the bike on it’s side stand, i believe that’s pointing me towards floats (argh lol)[quote]
- Rev up to 5000 rpm then let go, do you see any kind of smoke, do you smell any oil stench on the exhaust ? = too much engine oil , or concern for oil in engine (replace it, if the bike ever had fuel leak out of the carbs when it was OFF)
What seems to happen is the opposite, it will smoke a bit during idle and revving the bike causes it to clear up. I suspect it’s just so rich that the little smoke is actually from being super rich. it doesn’t smell oily to me
I see you have a full tank, buy WYNNS FORMULA GOLD PETROL (this bottle only) pour all in the tank, ride a bit and let us know if the bike starts to behave a little better as the fuel bars drop low. I trust the carbs are clean already but the WYNNS bottle might also make its way through the fuel lines, spark plugs , pistons ,to get some gunk off and take away some carbon (it will try!)
When i next fill up i’ll get some, currently there’s some redex in the tank :).
Plug Analysis
- Front center cone = main jet is OK, full throttle seems OK, but idling a bit rich due to dark black sooty ring but…..is the black ring oily or ashy-dusty ? – The plug’s threaded body looks dark at the base and almost silver rest of the way towards its white insulator, it means front cylinder isn’t overheating like crazy (thanks to winter and the nakedness of the GV!)
as for being black, it’s like ash, rather than oily.
Rear Center Cone + Rear RING = OK. Nothing to add here, it’s good! – This is the “aim” or sweet spot if you will. However, rear body of the plug suggests its a bit hotter than the front (threads are darker = hotter cylinder head but …. not concerning yet)
awesome 🙂 I’m not paying a huge amount of attention to the colour of the threads at the minute, they’re old plugs and were like that anyhow but i’m glad they not concerning 🙂
Throttle dipping / climbing means either these but we will narrow it down as we progress on servicing her…
- Mixtures , try to ride at 2.5 full turns out each cylinder and see how it generally rides. This will be our base as going beyond 3.5 turns is totally pointless , it will have less effect once you in full throttle (main jets and “slides” take over) so full throttle issues should be jets and slides (sticky?) …) or floats or fuel pump wanning or tap wanning , or the fuel parts have debris hence Wynns Formula in petrol to collect em and engine to burn them off out of the exhaust
My GV has 17.5 sized pilots, currently they’re both at 2 front and back. I wonder if the rear cylinder is a touch too lean at idle and needs a quarter turn more, and the front a quarter turn less.
Pilot Jet clogged again (revs flactuate) is a sign its “hunting” for fuel to prevent the bike stalling abruptly Starting = Permanent Jet + Pilot Jet = If you get access to air compressor , blow them hard
When cold the bike starts super easily, it’s actually harder when it’s warm
Fuel Levels = float heights , pilots “barely” reach the fuel but i think you know how to adjust them to a sweet spot by now 🙂 or i understand you’re experimenting with fatter aftermarket floats vs OEM ones but they still have max resting height of 7mm-8mm max . 7mm is the OEM sweet spot, i understand float needles and what not can affect the height a little bit , too much here or there can overflow fuel out of the carb so adjust and check accordingly. Richness = revs up, then dips below 1500 (see what i said prior to this sentence)
i’ll double check the floats, maybe my calliper is more a callipo than a mesuring tool lol
Needle of the Slide = If it has 5 steps to go down to the pointy tip, try step #5 , if its worse, go up to step 3 which is its default middle setting but never go beyond step 2 and 1 as those will lean out the bike. 5 step or 3 step needles Korea uses are always at the middle setting from factory. Going to the middle lets you see if full throttle makes it hit 70mph or not. More speed more fuel or too much fuel can bog it if rest of the bike isn’t optimized (air vs spark (all electrics from coils, plugs etc,) vs fuel (carb, tap, pump)
the front cylinder from stock is 4 and the rear being 3. I’ve left them at stock but maybe with the new jet it needs to be dialed back a touch on the front.
Full service is not a bad call! – You want to get to it before it gets too cold and Xmas is around the corner where families rob our time until new years lol I hope this reply made any sense but if at one point i confused you, just let me know , ill explain better next time
I’ve made a start on a service today, I’ve changed the Oil and filter. I also used the time to fit a 250 oil cooler 🙂 my oil lines were getting a bit frayed and looked quite rusty so it made sense to change them and do an OEM plus upgrade 🙂
I have yet to do the plugs or look at the mixtures. but I have a few jobs under the tank as well that when i have more light i’ll lump together.